Nested routes rendering with React-Router and Express is not working

Simple paths like /current are rendering fine on refresh, but as soon as a second layer is reached, /current/all for example, the console sends the following error:

Uncaught SyntaxError: Unexpected token <

The problem is caused by the browser using relative urls. The solution is to specify the base URL so that all path are defined relative to /. Adding <basehref="/"> in the head fixes the problem.

Solution on StackOverflow